Effective perinatal treatment strategies during the past 15 years have increased the survival of low birth weight infants. Accompanying this increased survival has been a 4-6 fold increase in the number of children surviving with bronchopulmonary dysplasia(BPD), although the birthweight specific incidence has remained constant or declined. Limited data currently available indicates that individuals who had BPD as infants have, as childrearing adults, impaired lung growth as well as both fixed and reversible airways obstruction. The long range goal of this study is to establish in children born prematurely a set of links between lung function in late infancy and lung function at school age, between lung function at school age and that in adolescence, and between lung function in adolescence and that in adulthood in order to evaluate pulmonary outcomes of neonatal therapeutic strategies and to relate these strategies to lung health in adult life. Based on available data, we hypothesize that BPD morbidity is related to impaired lung growth in the first year of life, does not improve during adolescence and is accentuated in females because of their intrinsically smaller lungs. To test this hypothesis measurements of lung size and airway function will be studied in teenagers and young adults, previously studied at school age, who were born, 1) at term, 2) prematurely, 3) developed respiratory distress syndrome of the newborn (RDS) or 4) developed BPD. Children born from 1987-89 previously studied at 10 months of age by novel lung function function methods developed in this laboratory will be restudied at school age. Techniques of measuring total respiratory system compliance and resistance and of obtaining forced expiratory flow at functional residual capacity will be applied to cohorts of currently born premature infants at 10-18 months of age to assess outcome of current perinatal strategies.